Oleophobic laminated articles, assemblies of use, and methods

ABSTRACT

An article, such as a filter or film, has a treated laminate with an expanded PTFE membrane and a porous support scrim. The treated laminate is formed by contacting a laminate having an expanded PTFE membrane and a porous support scrim with an oleophobic treatment agent dissolved in an organic solvent. The oleophobic treatment agent is deposited onto the expanded PTFE membrane and porous support scrim as the organic solvent is removed. The oleophobic treatment agent is typically a fluoropolymer. The article can be used, for example, as a filter over a port in a housing of an electronics or other device.

FIELD OF THE INVENTION

[0001] The present invention is, in general, directed to laminatedarticles including filters and films. More specifically, the inventionis directed to a laminated article, such as a filter, having a supportscrim, a membrane, and an oleophobic enhancement agent disposed from anorganic solvent onto the support scrim and membrane. The invention alsoconcerns assemblies using the laminated articles.

BACKGROUND OF THE INVENTION

[0002] Laminated articles have many uses, including, for example, asfilters and films. The laminated articles can be formed with a varietyof different properties which are often a result of the construction ofthe laminated articles. For example, appropriate materials and layerscan be used in forming the laminated articles to provide the desiredproperties. Properties of the laminated articles can also be modified bytreatments including, for example, chemical treatments. In a number ofapplications, laminated articles are useful as filters or protectivefilms that allow the flow of air into or through the laminated articlewhile preventing or restricting the flow of particulate matter, water,oil, other organic compounds, and/or other contaminants.

[0003] One example of a laminated article is a breather filter thatpermits the flow of a fluid, such as air, through the filter, butprevents or restricts the flow of particles and other contaminants(e.g., water and/or organic compounds). The filter typically includesone or more porous layers. The average pore size of the porous layer orlayers of the filter influences the size of particles that can flowthrough the filter.

[0004] In addition, one or more layers of the filter may be treated withor formed using a material to prevent or resist the flow of selectedcompounds or contaminants through or into the layer. For example, alayer may be treated with or formed using a hydrophobic material toresist the passage of water through or into that layer. Conversely, thelayer may be treated with or formed using a hydrophilic material. Othercircumstances call for a layer or layers that are oleophobic oroleophilic.

[0005] In some circumstances, there is a need to prevent or restrict theflow of a variety of particles and fluids. For example, filters andfilms are often used in environments that are sensitive to contaminantswith disparate properties, such as particulate matter, water, and oilymaterials. Such environments may include, for example, storagecontainers for oily materials and articles used near an engine. Thedisparate nature of the contaminants often requires the use of acombination of approaches to prevent or restrict the flow of thesematerials, including, for example, the choice of an appropriate averagepore size, the choice of materials for the layers of the laminatearticle, and the treatment of one or more layers of the laminatedarticle.

SUMMARY OF THE INVENTION

[0006] Generally, the present invention relates to laminated articles,methods of making the laminated articles, and assemblies using thelaminated articles. One embodiment is an article having a treatedlaminate with an expanded polytetrafluoroethylene (PTFE) membrane and aporous support scrim. The treated laminate is formed by contacting alaminate having an expanded PTFE membrane and a porous support scrimwith an oleophobic treatment agent dissolved in an organic solvent. Theoleophobic treatment agent is deposited onto the expanded PTFE membraneand porous support scrim as the organic solvent is removed. A filter maybe formed using the treated laminate.

[0007] Yet another embodiment is a method of making an article having anoleophobically-treated laminate. A laminate having an expanded PTFEmembrane and a porous support scrim is brought into contact with anoleophobic treatment agent dissolved in an organic solvent. Theoleophobic treatment agent is deposited onto the expanded PTFE membraneand porous support scrim as the organic solvent is removed.

[0008] A further embodiment is an assembly having a housing with a portto permit air flow into and out of the housing. A filter is disposedover the port to prevent or restrict the flow of contaminants. Thefilter includes a treated laminate with an expanded PTFE membrane and aporous support scrim. The treated laminate is formed by contacting alaminate having an expanded PTFE membrane and a porous support scrimwith an oleophobic treatment agent dissolved in an organic solvent. Theoleophobic treatment agent is then deposited onto the expanded PTFEmembrane and porous support scrim as the organic solvent is removed.

[0009] One example of the assembly is a headlamp for a vehicle. Theheadlamp includes a light source and a housing around the light source.The housing has a port to permit air flow into and out of the housingwith the filter having the treated laminate disposed over the port.

[0010] The above summary of the present invention is not intended todescribe each disclosed embodiment or every implementation of thepresent invention. The Figures and the detailed description which followmore particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention may be more completely understood in considerationof the following detailed description of various embodiments of theinvention in connection with the accompanying drawings, in which:

[0012]FIG. 1 is a cross-sectional view of one embodiment of a laminatedarticle, according to the invention;

[0013]FIG. 2 is a cross-sectional view of a second embodiment of alaminated article, according to the invention;

[0014]FIG. 3 is a cross-sectional view of a third embodiment of alaminated article, according to the invention;

[0015]FIG. 4 is a bottom view of the laminated article of FIG. 3;

[0016]FIG. 5 is a cross-sectional view of a fourth embodiment of alaminated article, according to the invention;

[0017]FIG. 6 is a cross-sectional view of a fifth embodiment of alaminated article, according to the invention;

[0018]FIG. 7 is a cross-sectional view of a sixth embodiment of alaminated article, according to the invention;

[0019]FIG. 8 is a cross-sectional view of an assembly with electroniccomponents utilizing any of the laminated articles of FIGS. 1-7; and

[0020]FIG. 9 is a cross-sectional view of a headlamp utilizing any ofthe laminated articles of FIGS. 1-7.

[0021] While the invention is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] The present invention is believed to be applicable to laminatedarticles, methods of forming laminated articles, and assemblies usinglaminated articles. In particular, the present invention is directed tolaminated articles, such as filters and films, that are oleophobic, aswell as methods of forming such laminated articles and assemblies usingthe laminated articles. While the present invention is not so limited,an appreciation of various aspects of the invention will be gainedthrough a discussion of the examples provided below. In particular, theinvention is described below in the context of a laminated article usedas a filter, however, it will be understood that the invention includesother laminated articles, such as films.

[0023] “Oleophobicity” of a laminated article can be rated on a scale of1 to 8 according to AATCC test 118-1992, incorporated herein byreference. This test evaluates an article's resistance to wetting. Eightstandard oils, labeled #1 to #8, are used in the test. The #1 oil ismineral oil (surface tension: 31.5 dynes/cm@25° C.) and the #8 oil isheptane (surface tension: 14.8 dynes/cm@25° C.). Five drops of eachrated oil are placed on the laminated article. Failure occurs whenwetting of the laminated article by a selected oil occurs within 30seconds. The oleophobic rating of a laminated article corresponds to thelast oil successfully tested. The higher the oleophobic rating, thebetter the oleophobicity.

[0024] An “increase in oleophobicity”, as the term is used herein,unless provided otherwise, generally refers to a comparison between atreated laminated article and an untreated laminated article that isotherwise similarly constructed.

[0025] Laminated Articles

[0026]FIG. 1 illustrates one embodiment of a laminated article 20 of theinvention. The laminated article 20 includes a membrane 22 and a supportscrim 24 laminated together. An oleophobic enhancement agent is disposedfrom an organic solvent onto the membrane 22 and the support scrim 24.Typically, the addition of an oleophobic enhancement agent increasesoleophobicity of the laminated article 20.

[0027] The Membrane

[0028] The membrane 22 is a microporous polymeric film to allow the flowof a fluid, such as air, into or through the membrane 22. A preferredpolymeric film for use as the membrane 22 includes expandedpolytetrafluoroethylene (PTFE) films, as described, for example, in U.S.Pat. Nos. 3,953,566; 4,187,390; 4,945,125; 5,066,683; 5,157,058; and5,362,553 incorporated herein by reference, or available commercially,for example, as Tetratec #1305 (Tetratec, Philadelphia, Pa.) orPoreflon™ WP-100, Sumitomo Electric Industries, Osaka, Japan. Anexpanded PTFE film typically comprises a plurality of nodesinterconnected by fibrils to form a microporous structure.

[0029] Expanded PTFE films for use in air filtering and otherapplications often have a relatively good air permeability. One measureof the air permeability of the expanded PTFE films is the number ofseconds required for the flow of 100 cubic centimeters of air throughthe film, according to the TAPPI T 460 om-96 test protocol, incorporatedherein by reference. Typically, the air permeability of suitableexpanded PTFE films is not greater than 20 seconds, as measured using aGurley densometer, Model No. 4110, Gurley Precision Instruments, Troy,N.Y. Preferably, the air permeability is not greater than about 6seconds and, more preferably, not greater than about 4 seconds.

[0030] Expanded PTFE films are typically hydrophobic. This property ofthe expanded PTFE films is generally useful in applications whererestriction of water or water vapor flow is desired. In many cases,suitable expanded PTFE films have a moisture vapor transmission ratio(MVTR) at 23° C. of, for example, about 1500 g/m²/24 hours or less, asmeasured according to ASTM E 96-95, incorporated herein by reference,using a Hotpack Temperature and Humidity Oven, Hotpack (Philadelphia,Pa.). Preferably, the MVTR is about 1400 g/m²/24 hours or less and, morepreferably, about 1250 g/m²/24 hours or less.

[0031] Another measure of water permeability is hydrostatic head (i.e.,the pressure required to push water through the film), according to ASTMD 715-95, Sections 37-41, incorporated herein by reference. Typically,the hydrostatic head for expanded PTFE films is no greater than about1000 kPa (about 150 p.s.i.) and is usually at least 7 kPa (about 1p.s.i.) In some embodiments, the hydrostatic head ranges from about 7kPa to about 900 kPa (about 1 to about 130 p.s.i.) and, preferably, fromabout 70 kPa to about 240 kPa (about 10 to about 35 p.s.i.).

[0032] The size of the pores contributes to determining the effectiverange of particles that can be prevented or restricted from flow throughthe laminated article 20. Often the average pore size of the membrane 22is about 2 μm or less. For many filtering applications, the average poresize ranges from about 0.05 μm to about 1.5 μm, preferably, from about0.2 μm to about 1.0 μm, and, more preferably, from about 0.5 μm to about0.8 μm. However, larger or smaller average pore sizes may be used.

[0033] Another factor in the flow of the fluid through the laminatedarticle is the porosity of the membrane 22, (i.e., the percentage ofopen space in the volume of the membrane 22, as determined by comparisonof the density of the membrane with respect to the density of nonporousPTFE). Typically, the porosity of the membrane 22 is about 20% orgreater and about 95% or less. Often the porosity of the membrane 22 ofa laminated article suitable for many filtering applications ranges fromabout 70% to about 95%, preferably from about 80% to about 95%, and morepreferably from about 85% to about 95%.

[0034] The dimensions (e.g., length, width, or diameter) of the membrane22 often depend on the use of the laminated article 20. For example, alaminated article 20 used as a breather filter typically covers a portthrough which a fluid, such as air, flows. The breather filter preventsor restricts the flow of selected particles and/or contaminants (e.g.,water and/or organic compounds) through the filter. The size of thebreather filter, and its components, such as the membrane 22 and supportscrim 24, are typically at least as large as the port. An absorbingfilter, in which the membrane or another layer absorbs a contaminant,such as water and/or organic compounds, often has dimensions related tothe amount of material to be absorbed during the lifetime of the filter.On the other hand, a film may include a membrane formed over a surfaceareas of a few square millimeters or less to a few square meters ormore.

[0035] The thickness of the membrane 22 may depend, for example, on theamount of filtering desired, the average pore size of the membrane 22,the expected or desired lifetime of the laminated article 20, theaverage pore size of other layers in the laminated article 20, and thedurability of the membrane 22 or other layer in the laminated article20. Generally, the thicker the membrane 22, the more restricted the flowof fluid and/or particles through the membrane 22. Thus, for example,the thickness of a membrane in a breather filter may be determined by abalance of a desired rate of mass transport of fluid (e.g., air) acrossthe membrane and a desired amount of filtration of contaminants (e.g.,particles, water, and/or oily materials). In some embodiments of theinvention, useful, for example, as filters, the thickness of themembrane is 500 μm or less and at least about 0.5 μm. For theseembodiments, the thickness of the membrane typically ranges from about 4μm to about 200 μm, preferably, from about 10 μm to about 150 μm, and,more preferably, from about 25 μm to about 100 μm. However, larger andsmaller thicknesses may be used.

[0036] The Support Scrim

[0037] Some membranes 22, including, for example, many expanded PTFEmembranes suitable for filtering applications, are thin and fragile. Asupport scrim 24 is usually included in the laminated article 20 toprovide support to the membrane 22. The support scrim 24 may have otheror alternative functions including, for example, restricting orpreventing the flow of the same and/or different particles and fluids asthe membrane 22 and/or protecting the membrane 22 or other layers in thelaminated article from damage. In some embodiments, a support scrim isnot needed.

[0038] The support scrim 24 is typically formed using a woven ornonwoven porous, polymeric material. Often the support scrim is madeusing a fibrous material, however, other porous materials may also beused. The average pore size of the support scrim 24 is usually largerthan the average pore size of the membrane 22, although this is notnecessary in some applications. Thus, in some embodiments, the supportscrim 24 acts to at least partially filter the fluid flowing into orthrough the laminated article. Typically, the average pore size of thesupport scrim is about 100 μm or less and often at least about 0.5 μm.The average pore size of support scrims suitable for many filteringapplications ranges from about 1 μm to about 50 μm, preferably, fromabout 7 μm to about 35 μm, and, more preferably, from about 10 μm toabout 30 μm. The porosity of the support scrim is often about 20% orgreater and typically no more than about 90%. The porosity of supportscrims suitable for many filtering applications often ranges from about20% to about 80%, preferably, from about 30% to about 75%, and, morepreferably, from about 40% to 70%.

[0039] Suitable polymeric materials for the support scrim 24 include,for example, stretched or sintered plastics, such as polyesters,polypropylene, polyethylene, and polyamides (e.g., nylon). Examples ofcommercially available nonwoven materials for use as a support scriminclude Hollytex™ #3257 from Ahlstrom Filtration, Inc. (Mount HollySprings, Pa.) and Cerex™ #100 from Midwest Filtration Company(Fairfield, Ohio) or Cerex Advanced Fabrics (Pensacola, Fla.). Thesematerials are often available in various weights including, for example,0.5 oz./sq.yd (about 17 g/m²), 1 oz./sq. yd (about 34 g/m²), and 2oz./sq. yd (about 68 g/m²). Examples of commercially available wovenmaterials for use as a support scrim include a polyester film (Style604, 150 denier) from Travis Textiles (New York, N.Y.).

[0040] Additional examples of support scrim materials are variousstretched or sintered polyethylene, polypropylene, and other plastics,including, for example, Exxaire XBF-110W, XBF-116W, BF-303W, andBF-513K2 from Exxon Corp. (Buffalo Grove, Ill.), AP3 materials fromAmoco Corp. (Atlanta, Ga.), X-7744 Porex T3 from Porex TechnologiesCorp. (Fairburn, Ga.), and BR-300 from Clopay Building Products Co.,Inc. (Cincinnati, Ohio). These same materials may also be used, in someembodiments, as a membrane instead of or in addition to the expandedPTFE membrane.

[0041] Lamination

[0042] The support scrim 24 and the membrane 22 are laminated together.The lamination of the support scrim 24 and the membrane 22 can beaccomplished by a variety of methods including, for example, heatlamination and adhesive lamination. FIG. 1 illustrates one embodiment ofa laminated article in which the support scrim 24 and membrane 22 areadhered by heat lamination.

[0043]FIG. 2 illustrates another embodiment of a laminated article 120having a laminating adhesive layer 126 disposed between at least aportion of a support scrim 124 and a membrane 122. The laminatingadhesive layer 126 may include any of a variety of temporary orpermanent adhesives including, for example, thermoplastic resins,thermosetting resins, cements, contact adhesives, and pressure sensitiveadhesives.

[0044] Oleophobic Enhancement Agent

[0045] Returning to FIG. 1, both the support scrim 22 and the membrane24 are treated using an oleophobic enhancement agent in an organicsolvent to increase the oleophobicity of the laminated article 20.Suitable oleophobic enhancement agents include fluoropolymers. A varietyof fluoropolymers are used or are known to be useful for treatingfabrics. These known fluoropolymers are also generally useful fortreating the support scrim 22 and expanded PTFE membrane 24 to increaseoleophobicity.

[0046] Examples of useful fluoropolymers include those having afluoroalkyl portion or, preferably, a perfluoroalkyl portion. Thesefluoropolymers include, for example, fluoroalkyl esters, fluoroalkylethers, fluoroalkyl amides, and fluoroalkyl urethanes. Often, thefluoroalkyl and/or perfluoroalkyl portion extends from a backbone of thepolymer.

[0047] The fluoropolymers may include a variety of monomer units.Exemplary monomer units include, for example, fluoroalkyl acrylates,fluoroalkyl methacrylates, fluoroalkyl aryl urethanes, fluoroalkyl allylurethanes, fluoroalkyl maleic acid esters, fluoroalkyl urethaneacrylates, fluoroalkyl amides, fluoroalkyl sulfonamide acrylates and thelike. The fluoropolymers may optionally have additional non-fluoromonomer units including, for example, unsaturated hydrocarbons (e.g.,olefins), acrylates, and methacrylates. Additional examples of suitablefluoropolymers are provided in U.S. Pat. No. 3,341,497, incorporatedherein by reference.

[0048] An exemplary, commercially-available fluoropolymer solution isFC-3537 from 3M Co. (St. Paul, Minn.). This solution contains 25 wt. %fluoropolymer, 57 wt. % heptane, and 18 wt. % ethyl acetate. The amountof fluoropolymer can be reduced by dilution using, for example, heptane(or another alkane), ethyl acetate, methyl isobutyl ketone, or othersolvents. Another exemplary, commercially-available fluoropolymersolution is FX-3539 from 3M Co. (St. Paul, Minn.). This polymer isdissolved in 9 wt. % dioctyladipate and 61 wt. % methyl isobutyl ketoneand contains 30 wt. % solids.

[0049] Other exemplary, commercially-available fluoropolymers areprovided in aqueous emulsions. Examples of these fluoropolymers includeFC-824, FC-808, and FC-280 from 3M Co. (St. Paul, Minn.) and Zonyl 9123(E.I. duPont de Nemours, Wilmington, Del.). The fluoropolymers can beextracted from the aqueous emulsion by removal of the water carrier. Thefluoropolymers can then be solvated in an organic solvent. For example,the fluoropolymer of FC-824 or Zonyl 9123 can be solvated in methylisobutyl ketone or other solvents after removal of the water. Tofacilitate the solvation of the fluoropolymer, a compound, such asacetone, can be optionally added to the aqueous emulsion to break theemulsion. In addition, the particles of fluoropolymer can be optionallyground, subsequent to removal of water to make solvation easier andquicker.

[0050] Organic Solvents for the Oleophobic Enhancement Agent

[0051] A variety of organic solvents can be used in the solutioncontaining the oleophobic enhancement agent. Typically, the term“organic solvent” refers to non-aqueous solvents and combinations ofnon-aqueous solvents, and, in particular, to solvents comprising organiccompounds. As used herein, a material is “dissolved in an organicsolvent” if 100 wt. % of the material is dissolved in the organicsolvent, unless otherwise indicated.

[0052] In many preferred embodiments, the oleophobic enhancement agentis dissolved in the organic solvent. In other embodiments, theoleophobic enhancement agent is not fully dissolved into the organicsolvent. In these embodiments, a portion of the oleophobic enhancementagent may remain out of solution or may be dispersed or dissolved in anaqueous solvent. Typically, at least 50 wt. % of the oleophobicenhancement agent is dissolved in the organic solvent, preferably, atleast 75 wt. % of the oleophobic enhancement agent is dissolved in theorganic solvent, more preferably, at least 90 wt. % of the oleophobicenhancement agent is dissolved in the organic solvent, and, mostpreferably, at least 95 wt. % of the oleophobic enhancement agent isdissolved in the organic solvent. In these embodiments, thenon-dissolved oleophobic enhancement agent may optionally be removedfrom the solution.

[0053] In many preferred embodiments, the solution of the oleophobicenhancement agent and organic solvent does not include water. In otherembodiments, the solution may inadvertently or purposefully includewater, however, at least a portion of the oleophobic enhancement agentis dissolved in the organic solvent. In these embodiments, preferably,at least 75 wt. %, more preferably, at least 90 wt. %, and, mostpreferably, at least 95 wt. %, of the oleophobic enhancement agent isdissolved in the organic solvent. In these embodiments, the solutioncontains no more than 50 wt. % of water, preferably, no more than 75 wt.% of water, more preferably, no more than 90 wt. % of water, and, mostpreferably, no more than 95 wt. % or water.

[0054] Suitable organic solvents include, for example, alkanes, ketones,esters, ethers, alcohols, and the like, as well as combinations of thesesolvents. Suitable organic solvents include, for example, heptane,ethylacetate, butylacetate, isoamylacetate, dioctyladipate, acetone,methyl ethyl ketone, methyl isobutyl ketone, isopropanol, diethylether,mineral spirits, petroleum distillate (b.p. 100-140° C.), andcombinations thereof. A choice of solvent or solvents may be affected bya variety of factors including solubility of the fluoropolymer, boilingpoint of the solvent, molecular weight of the solvent, and polarity ofthe solvent or solvent combination.

[0055] For example, the boiling point of a suitable solvent is typicallybelow the melting point of the treated support scrim 24 and/or membrane24 and, preferably, below a temperature at which the treated supportscrim 24 and/or membrane 24 softens, particularly, if the solvent is tobe removed by heating after treatment of the layers of the laminatedarticle 20. For some embodiments, particularly those embodiments withpolyethylene or polypropylene support scrims and/or membranes, theboiling point of the solvent is typically below about 130° C., andpreferably ranges from about 30° C. to about 125° C., and, morepreferably, from about 40° C. to 110° C.

[0056] In some embodiments, the solvent or combination of solvents ischosen to have a relatively high vapor pressure, to facilitate removalby air drying or heating. In these embodiments, the vapor pressure at20° C. of the solvent or combination of solvents is 1 kPa or more,preferably, 3 kPa or more, and, more preferably, 5 kPa or more.

[0057] The amount of fluoropolymer in the solution may vary over a widerange. Typically, the amount of fluoropolymer in the solution affectsthe oleophobicity of the final product. In some cases, however, a largeamount of fluoropolymer deposited on the support scrim 24 and/ormembrane 22 can block the pores in these layers. Typically, the amountof fluoropolymer in the solution is about 25 wt. % or less, preferably,about 10 wt. % or less, and, more preferably, about 5 wt. % or less. Toprovide adequate coverage, the amount of fluoropolymer in the solutionis typically about 0.01 wt. % or more, preferably, about 0.05 wt. % ormore, and, more preferably, about 0.1 wt. % or more. For many filterapplications, the amount of fluoropolymer in the organic solvent rangesfrom about 0.01 wt. % to about 5 wt. %, preferably, from about 0.05 wt.% to about 3 wt. %, and, more preferably, from about 0.1 to about 2 wt.% of the solution.

[0058] Oleophobic Treatment

[0059] The support scrim 24 and membrane 22 may be treated with theoleophobic enhancement agent separately prior to lamination. Preferably,both the support scrim 24 and membrane 22 are treated togethersubsequent to lamination of the support scrim 24 and membrane 22.Typically, during treatment, the fluoropolymer solution wets and,preferably, saturates, the support scrim 24 and membrane 22. The solventis then removed, for example, by air drying or heating. The oleophobicenhancement agent couples to the support scrim 24 and/or membrane 22 andtypically imparts oleophobicity to the layer(s).

[0060] Optionally, the treated laminated article may be “cured” byheating. Although no theory is necessary to the invention, this “curing”process is believe to increase the oleophobicity by allowingrearrangement of the fluoropolymer into a preferred oleophobicorientation. The curing temperature varies among fluoropolymers, buttypically ranges from about 40° C. to about 140° C., preferably, fromabout 50° C. to about 130° C., and, more preferably, from about 70° C.and about 125° C.

[0061] After treatment and removal of the solvent, the laminated article20 usually has an increased oleophobicity. Typically the oleophobicrating of the laminated article 20 is at least 1, usually, at least 2,preferably, at least 4, more preferably, at least 6, and, mostpreferably, at least 8, as measured using AATCC test 118-1992.Typically, the treated laminated article has an increase of at least 1rating point above a similar untreated laminated article. Preferably,the increase in oleophobic rating is at least 2 rating points, morepreferably, at least 4 rating points, even more preferably, at least 6rating points, and, most preferably, 8 rating points.

[0062] The use of an organic solvent facilitates the distribution of thefluoropolymer throughout the support scrim 24 and/or membrane 22. Manypolymeric films, and, in particular, PTFE films, are not initiallyoleophobic and may be oleophilic. Thus, using of an organic solventoften reduces difficulties in wetting and/or saturating the supportscrim 24 and membrane 22 with the oleophobic enhancement agent solution.

[0063] Known Oleophobic Treatments

[0064] Known oleophobic treatments for expanded PTFE membranes use anaqueous emulsion of fluoropolymer particles. Expanded PTFE membranes aretypically hydrophobic. This suggests that wetting and saturating thesupport scrim 24 and/or membrane 22 using an aqueous emulsion may bedifficult and could result in a non-uniform coverage of the supportscrim 24 and/or membrane 22.

[0065] Moreover, expanded PTFE membranes are typically oleophilic. Thus,it is often desirable that an oleophobic treatment agent be distributedthroughout the membrane to reduce the oleophilic nature of the entiremembrane. Surface treatment of the membrane may not be sufficient. Thehydrophobicity of the expanded PTFE membrane creates difficulties indistributing an aqueous emulsion of fluoropolymer particles throughoutthe membrane.

[0066] Furthermore, the preferred method of treating the membraneincludes laminating the membrane to the support scrim prior to treatment(due, at least in part, to the fragile nature of typical expanded PTFEmembranes). It is believed, although no theory is necessary to theinvention, that if the membrane is not entirely treated with theoleophobic treatment agent, particularly at the interface between themembrane and the support scrim, oil or other contaminants may be wetinto the membrane, after sufficient force is applied to overcome theoleophobically-treated support scrim, due to the membrane's inherentoleophilicity.

[0067] To treat the interface between the membrane and the support scrimusing the known techniques, an oleophobic treatment agent in an aqueousemulsion must move through the support scrim and into the membrane. Thehydrophobicity of the membrane suggests that this may be difficult whenusing an aqueous emulsion of particles. Moreover, the use of suspendedparticles rather than solvated molecules suggests that the particles mayalso be hindered when flowing through the support scrim to adhere to themembrane and when orienting to attach to the membrane. In addition, itis thought that the use of an aqueous emulsion of fluoropolymer mayresult in a non-uniform distribution of fluoropolymer because thefluoropolymer in an aqueous emulsion is provided in the form ofparticles and not uniformly distributed as in a solution.

[0068] The use of an oleophobic enhancement agent in an organic solvent,as described herein, overcomes these concerns. The expanded PTFEmembrane can be wetted and saturated using organic solvents. Thus, thesolvated oleophobic enhancement agent can be distributed throughout themembrane. In addition, solvation of the oleophobic enhancement agenttypically provides a relatively uniform distribution of the agentthroughout the membrane. Treating one or more layers of a laminatedarticle with a fluoropolymer in an organic solvent provides astructurally different product in which the fluoropolymer is uniformlydistributed over the one or more layers instead of deposited asindividual particles.

[0069] Additional Examples of Laminated Articles

[0070]FIG. 3 illustrates another embodiment of a laminated article 220with a membrane 222, a support scrim 224, an adhesive layer 228 forattaching the laminated article 220 to a surface, and an optionalrelease liner 230 to prevent the adhesive layer 228 from adhering to asurface until desired. The adhesive layer 229 can include a variety ofpermanent or temporary adhesives including, for example, thermoplasticresins, thermosetting resins, cements, contact adhesives, and pressuresensitive adhesives. The adhesive layer 228 can be applied to either themembrane 222 (as illustrated in FIG. 3), support scrim 224, or both orto any other layer of the laminated article. The adhesive layer 228 maycover all or only a portion of the layer or layers of the laminatedarticle 220 to which the adhesive layer 228 is applied.

[0071] The release liner 230 is typically formed of a material laminatedarticle 220 can be removed while retaining at least a portion, and,preferably, substantially all, of the adhesive layer 228. Suitablematerials for the release layer include, for example, waxed paperproducts and polymeric films, such as Mylar™. In some embodiments, arelease liner is not used and/or necessary.

[0072] At least one embodiment of the laminated article 220 of FIG. 3 isuseful, for example, as a breather filter. In this embodiment, thelaminated article 220 has a portion 232 of the membrane that is coveredby the adhesive layer and another portion 234 that is not covered, asshown in FIG. 4. In operation, the breather filter is placed over a portin a surface so that a portion (preferably, at least the portion 234that is not covered by the adhesive layer) of the membrane covers theport. A fluid stream (e.g., air) may then flow through the breatherfilter with contaminants (e.g., particulate matter, water, and/or oilymaterials) being prevented or restricted from flowing through the port.

[0073]FIG. 5 illustrates another embodiment of a laminated article 320having a membrane 322 laminated to a support scrim 324 by a laminationadhesive layer 326. The laminated article 320 also includes an adhesivelayer 328 to adhere the laminated article to a surface and an optionalrelease liner 330.

[0074]FIG. 6 illustrates yet another embodiment of a laminated article420 having a membrane 422 and a support scrim 424. The laminated articlealso includes an adsorbent layer 436 and an optional support layer 438,an optional adhesive layer 428, and an optional release liner 430. Thislaminated article 420 is suitable for use, for example, as a filter orprotective film.

[0075] The adsorbent layer 436 typically adsorbs, absorbs, and/orreactively removes contaminants, such as, for example, organic moleculesand water, from a fluid stream. For example, the adsorbent layer 436 mayinclude active carbon to adsorb, absorb, or reactively remove organicmolecules. The adsorbent layer 436 may, for example, include ahydrophilic material, such as a silica gel or cotton fibers, to adsorband/or absorb water. Other adsorbent materials may also be used. Thethickness of the adsorbent layer 436 often depends on the projectedmaximum amount of material to be absorbed.

[0076] An optional support layer 438 may be used to support theadsorbent layer 436 and/or to prevent material (e.g., carbon particles)of the adsorbent layer 438 from escaping the laminated article. Thesupport layer 438 may be made using the same materials and methods asthe support scrim 424 or the membrane 422. The support layer 438 may ormay not be treated with oleophobic enhancement agent.

[0077]FIG. 7 illustrate a further embodiment of a laminated article 620that includes a membrane 622, a support scrim 624, an adhesive layer 628for adhering to a surface, and an optional release liner 630. Inaddition, the laminated article 620 includes a stiffness-enhancing layer640 and a second adhesive layer 642. The stiffness-enhancing layer 640is typically made of a material that enhances the stiffness of thelaminated article. Such materials include, for example, Mylar™.

[0078] In other embodiments, a support scrim of, for example, thelaminated article 20 of FIG. 2, is an adsorbent layer. In otherembodiments, an adsorbent layer is positioned between a support scrimand a membrane. In yet other embodiments, only one of the membrane andthe support scrim is treated with the oleophobic enhancement agent.

[0079] It will also be understood that laminated articles using othermembranes may also be treated in the same or similar manner to obtain alaminated article with increased oleophobicity. Examples of othermembranes include polypropylene, polyethylene, polyester, and otherplastic or polymeric microporous membranes, as well aspolytetrafluoroethylene membranes using forms of PTFE otherthan-expanded PTFE. Examples of such membranes include Exxaire XBF-110W,XBF-116W, BF-303W, and BF-513K2 from Exxon Corp. (Buffalo Grove, Ill.),AP3 materials from Amoco Corp. (Atlanta, Ga.), X-7744 Porex T3 fromPorex Technologies Corp. (Fairburn, Ga.), and BR-300 from ClopayBuilding Products Co., Inc. (Cincinnati, Ohio).

[0080] The Laminated Article used as a Filter

[0081] One application of the laminated articles, as described above, isas a filter. The filter is formed to prevent or restrict the flow ofparticulate matter, water, oil and/or similar molecules through thelaminated article, while allowing air flow. In one embodiment, a filterof the invention has an air permeability of about 8 seconds or less,according to TAPPI T 460 om-96. Preferably, the air permeability of thefilter is about 6 seconds or less, and, more preferably, about 3 secondsor less.

[0082] In one embodiment, a filter of the invention has a hydrostatichead measurement, according to ASTM D 715-95, Sections 37-41, of about900 kPa (about 130 p.s.i.) or less. Preferably, the hydrostatic headmeasurement of the filter is about 630 kPa (about 90 p.s.i.) or less,and, more preferably, about 310 kPa (about 45 p.s.i.) or less.

[0083] In one embodiment, a filter of the invention has an oleophobicrating of 1 or more, as measured according to AATCC test 118-1992.Preferably, the oleophobic rating of the filter is 2 or more, morepreferably, 4 or more, even more preferably, 6 or more, and, mostpreferably, 8 or more.

[0084] Filter Applications

[0085] As an example, a laminated article of the invention could be usedas a filter in an electronic device 450, as illustrated in FIG. 8.Typically, the electronic device 450 includes electronic or electricalcomponents 452 in a housing 454. In addition, the housing 454 typicallyhas a port 456 through which air is allowed to flow. The flow of air isoften desirable to prevent air pressure differentials between theinterior and exterior of the housing, for example, when the electronicor electrical components heat or cool during operation or when theelectronic device is carried in the cargo hold of an airplane. Moreover,the port 456 may be used to provide air to cool the electronic orelectrical components. Although, the port 456 is illustratedschematically as a direct flow-through port in the housing, it will beunderstood that, at least in some embodiments, the port 456 may includea tortuous, winding, or otherwise non-direct path for air flow.

[0086] To prevent the flow of contaminants, such as particulate matter,water, oil, other organic compounds, and/or other contaminants, eitherout of or into the housing 454, a filter 458 is provided over the port456. The oleophobic laminated articles, as described above, are usefulfilters 458 in this context.

[0087] Examples of electronic devices in which the oleophobic laminatedarticles of the invention can be used as a filter include oil sensor,disk drives, gas sensors, optical sensors, pressure transducers,headlight breather filters, cellular phone filters, and motors.

[0088] The use of the laminated articles is not restricted to electronicdevices. Other assemblies use filters to permit air flow through a portin the housing. Examples of these assemblies include sterile packaging,other packaging, medical devices, chain saw vents, ink-jet cartridges,chemical vents, anti-lock braking system (ABS) vents, and air bags.

[0089] One application of a filter made using the laminated article ofthe invention is in the context of a headlamp for a vehicle, such as,for example, a car, bus, motorcycle, or truck. A headlamp 500, asillustrated in FIG. 9, includes a light source 502 and a housing 504around the light source to protect the light source from damage andwater. Pressure differentials, caused, for example, by heating orcooling of the light source 502, can damage the light source 502 if oneor more ports 506 are not provided in the housing 504. Although, the oneor more ports 506 are illustrated schematically as direct flow-throughports in the housing, it will be understood that, at least in someembodiments, the one or more ports 506 may include a tortuous, winding,or otherwise non-direct path for air flow.

[0090] If the ports 506 are left open then particulate matter, water,oil, and/or other contaminants can enter the housing and damage thelight source or cloud the interior of the headlamp 500. Particulatematter, water, and oil are all relatively abundant in the environment ofa vehicle. Thus, one or more filters 508 are placed over the ports 506to prevent or restrict the flow of particulate matter, water, and oilinto the housing 504 while allowing the flow of air. Any of thelaminated articles illustrated in FIGS. 2-6 are useful as the filters508. Preferably, the average pore size of the membrane is 1 μm or lessto prevent or restrict the flow of particulate matter. The membrane ismade using a hydrophobic material, preferably, expanded PTFE, to preventor restrict the flow of water through the filters 508. In addition, themembrane and support scrim are treated with fluoropolymer solution tomake the filters 508 oleophobic to prevent or restrict the flow of oiland similar molecules through the filters 508.

EXAMPLES Example 1

[0091] Preparation of Fluoropolymer-Treated Laminated Articles.

[0092] Three laminated articles 1-A, 1-B, and 1-C were formed. Afluorocarbon polymer solution FC-3537 (3M Co., St. Paul, Minn.),containing 25 wt. % fluoropolymer in 57 wt. % heptane and 18 wt. % ethylacetate, was diluted by the addition of heptane to form individualsolutions with 0.1, 0.5, and 1.0 wt. % fluoropolymer, respectively, asshown in Table 1. Three support scrims, 1 oz. Hollytex #3257 (AhlstromFiltration, Inc., Mount Holly Springs, Pa.), were each laminated to oneof three membranes, Tetratec #1305 expanded polytetrafluoroethylene film(Tetratec, Philadelphia, Pa.), using an adhesive, Adhesive Pur-fect Lok34-9013 (National Starch and Chemical Corp., Bridgewater, N.J.). Thelaminated support scrims and membranes were then individually saturatedwith one of the diluted fluoropolymer solutions. The laminated layerswere allowed to air dry and then cured at about 116° C. for 1 minute.The amount of fluoropolymer on the laminated article was determinedusing the weight of the laminated support scrim and membrane a) prior tosaturation with the diluted fluoropolymer solution and b) after curing.Results are reported in Table 1.

[0093] An untreated laminated article is provided as a comparison. Theuntreated laminated article was formed by laminating a support scrim, 1oz. Hollytex #3257, to a membrane, Tetratec #1305 expandedpolytetrafluoroethylene film, using an adhesive, Adhesive Pur-fect Lok34-9013. TABLE 1 Fluoropolymer-Treated Laminated Articles Amount ofCalculated Amount Fluoropolymer in of Fluoropolymer in Diluted TreatingLaminated Article, Permeability, Laminated Solution, Wt. % of LaminatedOleophobic Gurley seconds, Article Wt. % of Solution Article Rating 100cc Untreated N.A. N.A. 0 2.7 1-A 0.1 0.18 2 1.8 1-B 0.5 0.78 4 2.2 1-C1.0 1.70 6 2.4

[0094] The oleophobic rating for each laminated article was obtainedusing AATCC test 118-1992. The higher the rating, the better theoleophobicity. The results are reported in Table 1 and indicate that theoleophobicity of the laminated articles increases with increasingamounts of fluoropolymer in the treating solution.

[0095] The air permeability of each laminated article was also measuredusing TAPPI T 460 om-96. The results are reported in Table 1. Treatingthe laminated article has little effect on air permeability.

Example 2

[0096] Preparation of Laminated Articles with Fluoropolymer-TreatedSupport scrims.

[0097] Three laminated articles 2-A, 2-B, and 2-C were formed. Afluorocarbon polymer solution FC-3537 (3M Co., St. Paul, Minn.),containing 25 wt. % fluoropolymer in 57 wt. % heptane and 18 wt. % ethylacetate, was diluted by the addition of heptane to form individualsolutions with 0.1, 0.5, and 1.0 wt. % fluoropolymer, respectively, asshown in Table 2. Three different support scrims, 1 oz. Hollytex #3257(Ahlstrom Filtration, Inc., Mount Holly Spring, Pa.), were treated withone of the three diluted fluoropolymer solutions. The support scrimswere allowed to air dry and then cured at a temperature of about 116° C.for 1 minute. Each support scrim was then laminated to an individualmembrane, Tetratec #1305 expanded polytetrafluoroethylene film(Tetratec, Philadelphia, Pa.), using an adhesive, Adhesive Pur-fect Lok34-9013 (National Starch and Chemical Corp., Bridgewater, N.J.). Theamount of fluoropolymer on the laminated article was determined usingthe weight of the support scrim and membrane a) prior to saturation ofthe support scrim with the diluted fluoropolymer solution and b) afterlamination of the support scrim to the membrane. Results are reported inTable 2. TABLE 2 Laminated Articles with Fluoropolymer-Treated Supportscrims Amount of Calculated Amount Fluoropolymer in of Fluoropolymer onDiluted Treating Laminated Article, Permeability, Laminated Solution,Wt. % of Laminated Oleophobic Gurley seconds, Article Wt. % of SolutionArticle Rating 100 cc Untreated N.A. N.A. 0 2.7 2-A 0.1 0.088 2 3.2 2-B0.5 0.39 2 3.1 2-C 1.0 0.61 2 2.8

[0098] An oleophobic rating for each laminated article was obtainedusing AATCC test 118-1992, as described above. The results are reportedin Table 1. An oleophobic rating was also measured for the support scrimprior to lamination to the membrane. The measured oleophobic rating forthe support scrim of each of the treated laminated articles was 8.

[0099] The air permeability of each laminated article was also measuredusing TAPPI T 460 om-96. The results are reported in Table 1. Treatingthe laminated article has little effect on air permeability.

[0100] The present invention should not be considered limited to theparticular examples described above, but rather should be understood tocover all aspects of the invention as fairly set out in the attachedclaims. Various modifications, equivalent processes, as well as numerousstructures to which the present invention may be applicable will bereadily apparent to those of skill in the art to which the presentinvention is directed upon review of the instant specification.

I claim:
 1. An article comprising: a treated laminate of an expandedPTFE membrane and a porous support scrim, the treated laminate resultingfrom (i) contacting a laminate of an expanded PTFE membrane and a poroussupport scrim with an oleophobic treatment agent dissolved in an organicsolvent; and (ii) depositing the oleophobic treatment agent onto theexpanded PTFE membrane and porous support scrim, wherein depositing theoleophobic treatment agent comprises removing the organic solvent. 2.The article of claim 1, wherein the treated laminate further resultsfrom heat treating the laminate to orient the oleophobic treatmentagent.
 3. The article of claim 1, wherein the treated laminate resultsfrom immersing a laminate of an expanded PTFE membrane and a poroussupport scrim in an oleophobic treatment agent dissolved in an organicsolvent.
 4. The article of claim 1, wherein the treated laminate resultsfrom saturating a laminate of an expanded PTFE membrane and a poroussupport scrim with an oleophobic treatment agent dissolved in an organicsolvent.
 5. The article of claim 1, wherein the treated laminate resultsfrom depositing the oleophobic treatment agent throughout the expandedPTFE membrane and porous support scrim.
 6. The article of claim 1,wherein the oleophobic treatment agent comprises a fluoropolymer.
 7. Thearticle of claim 1, wherein the support scrim comprises a polymericmaterial.
 8. The article of claim 7, wherein the polymeric materialcomprises polypropylene, polyethylene, polyester, or nylon.
 9. Thearticle of claim 1, wherein the support scrim and the expanded PTFEmembrane are laminated together by heat.
 10. The article of claim 1,further comprising an adhesive between the support scrim and theexpanded PTFE membrane to laminate the support scrim and the expandedPTFE membrane together.
 11. The article of claim 1, further comprisingan adhesive disposed on the expanded PTFE membrane for adhering thearticle to a surface.
 12. A filter comprising: a porous treated laminateof an expanded PTFE membrane and a porous support scrim, the poroustreated laminate resulting from (i) contacting a porous laminate of anexpanded PTFE membrane and a porous support scrim with an oleophobictreatment agent dissolved in an organic solvent; and (ii) depositing theoleophobic treatment agent onto the expanded PTFE membrane and poroussupport scrim, wherein depositing the oleophobic treatment agentcomprises removing the organic solvent.
 13. The filter of claim 12,further comprising an adsorbent layer laminated to the expanded PTFEmembrane.
 14. The filter of claim 13, further comprising a support layerlaminated to the adsorbent layer.
 15. The filter of claim 12, furthercomprising adhesive disposed on the filter to adhere the filter to asurface.
 16. A method of making an article having an oleophobic-treatedlaminate, the method comprising: contacting a laminate of an expandedPTFE membrane and a porous support scrim with an oleophobic treatmentagent dissolved in an organic solvent; and depositing the oleophobictreatment agent onto the expanded PTFE membrane and porous supportscrim, wherein depositing the oleophobic treatment agent comprisesremoving the organic solvent.
 17. The method of claim 16, furthercomprising heat treating the laminate to orient the oleophobic treatmentagent.
 18. The method of claim 16, wherein contacting a laminatecomprises saturating a laminate of an expanded PTFE membrane and aporous support scrim with an oleophobic treatment agent dissolved in anorganic solvent.
 19. An assembly comprising: a housing having a port forair flow; and a filter disposed over the port, the filter comprising atreated laminate of an expanded PTFE membrane and a porous supportscrim, the treated laminate resulting from (i) contacting a laminate ofan expanded PTFE membrane and a porous support scrim with an oleophobictreatment agent dissolved in an organic solvent; and (ii) depositing theoleophobic treatment agent onto the expanded PTFE membrane and poroussupport scrim, wherein depositing the oleophobic treatment agentcomprises removing the organic solvent.
 20. The assembly of claim 19,wherein the assembly is a headlamp and the assembly further comprises alight source disposed in the housing.